Re: Dirac String Trick

[Hugh Haskell <hhaskell@MINDSPRING.COM>]

> "John S. Denker" wrote:
> >  (This works with three strings, or any larger number.)
>
> Three strings on each side (left and right, the way you drew it), or
> three strings total?
>
> >  ================
> >
> >  Also:  The Philippine Wine Glass Trick is almost as much fun as the Dirac
> >  String Trick.
> >
> >  Some hints:
> >
> >  2) For the first 2pi of rotation, tuck it under your elbow.  For the second
> >  2pi of rotation, it passes above the same elbow.  It's an unfamiliar
> >  motion, but perfectly doable.
>
> Okay, I'll take the bait. Either my arm is insufficiently flexible to
> pass the cup below my elbow, or I'm doing something wrong. I have a
> feeling it is the latter. I did try, though, although I had to give up
> when my elbow started to hurt. :-)
>
> --MB

I've been doing that trick for some time, but it's hard to describe.
You really need to see someone do it. The first rotation (under your
elbow) leaves your hand kind of "upside down" when you finish, and
its a bit uncomfortable. But if you always keep you palm as near
upright as you can, and continue the rotation in the same sense, but
this time bringing your palm over your head, you will end up with
your hand in the same position it was at the beginning. I don't
recommend doing it with a full glass the first few times you try. In
fact, you can get the idea if you leave your hand empty, but open
with palm up throughout.

I suspect that the explanation of this trick is closer to quaternions
than fermions. There is an fairly complete geometric explanation of
this type of rotation in the book "Icons and Symmertries," by Simon
L. Altman (London: Oxford University Press, 1992, ISBN:
0-19-855599-7), pp. 55 ff.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

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